If you are referring to one of the cable guides (which I'm pretty sure you are since your window fell down) you are going to need the entire window regulator. Good news is, they are commonly stocked, and relatively cheap. Super easy to replace too.

I've replaced both front window regulators. There is more than one type. I got the wrong one the first time and had to exchange it. Take the door apart to be sure which one you have. Good service from RockAuto.

I have Replaced the window regulator on my durango multiple times. Front driver side 3x front passenger side 2x rear drivers side x1 and now just tonight rear passenger side broke for the second time. I can replace them now blindfolded and one hand tied behind my back. I wish there was some replacement that was guaranteed not to break